There have been thin-film solar cells including a light-absorbing layer using: CuInSe2 being a compound-semiconductor film of a chalcopyrite structure composed of a Group-Ib, a Group-IIIb, and a Group-VIb element (that is a CIS-based film); or Cu(In, Ga)Se2 being a solid solution thereof with Ga as a solute (that is a CIGS-based film). They have been adapted for high efficiencies of energy conversion with reduced deteriorations of efficiency such as due to light irradiation, as an advantage.
There have been literatures (cf. Patent Literature 1 and Patent Literature 2) disclosing photoelectric conversion devices employing a compound-semiconductor film of chalcopyrite structure with a greatly reduced dark current, and fabrication methods thereof.
Also, there have been literatures (cf. Patent Literature 3 and Patent Literature 4) disclosing methods of formation such as by selenidation of a high-quality CIGS-based film.
Also, there has been a literature (cf. Non-Patent Literature 1) disclosing effects of surface Cu2-xSe layers on growth and properties of CuInSe2 films.